The present invention relates to a tire/wheel assembly and a run-flat support member, and more specifically to a tire/wheel assembly and a run-flat support member having superior durability during run-flat traveling.
In response to demands from the market, there have been many technologies proposed to allow a vehicle to run urgently for several hundreds of kilometers even when a pneumatic tire is punctured while the vehicle is running. Amongst these many proposals, technologies proposed in Japanese Patent Laid-Open Publication No. 10-297226 and Published Japanese Translation of a PCT Application No. 2001-519279 enable run-flat traveling by fitting a core onto a rim in the inner side of a cavity of a pneumatic tire that is assembled to the rim, and by supporting the punctured tire using the core.
The foregoing run-flat core includes a circular shell in which the outer circumferential side thereof serves as a support surface and the inner circumferential side thereof is opened so as to form two leg portions. Also, elastic rings are fitted to both leg portions of the circular shell, thus the run-flat core is supported on the rim through the elastic rings. By using respect to this run-flat core, a conventional wheel and rim can be used as they are without any particular modifications. Therefore, the run-flat core is advantageously adopted without causing confusion in the market.
However, during run-flat traveling, the above tire/wheel assembly (wheel) runs while supporting a load mainly by the circular shell. Therefore, fatigue appears in the circular shell first, and the circular shell in due course will break after driving a long distance or being repeatedly used over a number of times. If the circular shell is broken, run-flat traveling becomes no longer possible. Hence, the life span of the above tire/wheel assembly depends on durability of the circular shell. Accordingly, in order to extend a run-flat traveling, it is important to increase the durability of the circular shell to a feasible extent.
An object of the present invention is to provide a tire/wheel assembly which improves durability of a circular shell and enables a run-flat traveling distance to be further extended. Another object of the present invention is to provide a run-flat support member which improves durability of a circular shell and enables a run-flat traveling distance to be further extended.
In the tire/wheel assembly of the present invention for achieving the above object, a run-flat support member is inserted in a cavity of a pneumatic tire, where the run-flat support member includes a circular shell in which the outer circumferential side thereof is used as a support surface and the inner circumferential side thereof is opened to have two leg portions, and elastic rings for supporting the ends of the two leg portions on the rim. This tire/wheel assembly is characterized in that the outer circumferential surface of the circular shell in a cross-section cut in a tire width direction has a shape with a plurality of convex portions aligned in a tire width direction, and that the convex portions have a plurality of different kinds of radius of curvatures and/or thickness.
Moreover, the run-flat support member of the present invention includes a circular shell in which the outer circumferential side thereof is used as a support surface and the inner circumferential side thereof is opened to have two leg portions, and elastic rings for supporting the ends of the two leg portions on the rim. The run-flat support member is characterized in that the outer circumferential surface of the circular shell in a cross-section cut in a tire width direction has a shape with a plurality of convex portions aligned in a tire width direction, and that the convex portions have at least two different kinds of radius of curvatures and/or thickness.
According to the present invention, as described above, the outer circumferential surface of the circular shell in a cross-section cut in a tire width direction has the shape with the plurality of convex portions aligned in a tire width direction, and the convex portions have a plurality of different kinds of radius of curvatures and/or thickness. Consequently, a convex portion that has a smaller radius of curvature or a larger thickness compared to those of the other convex portions has higher rigidity compared to the other convex portions. Therefore, by disposing the convex portion having higher rigidity so as to come to a position where the largest load is applied in a tire width direction, durability of the circular shell is improved and a run-flat traveling distance can be extended.
In many cases, a wheel alignment has positive camber. Because of this, a load distributed in a direction of tire tread width, in particular, is applied intensively to outer sides of a vehicle body. Therefore, amongst the plurality of convex portions forming the circumferential surface of the circular shell, a convex portion disposed on an outer side of a vehicle body when fitted to the vehicle is formed to have a radius of curvature smaller than that of other convex portions. Alternatively, a convex portion disposed on an outer side of a vehicle body when fitted to the vehicle is formed to have a peak and/or sidewall on the outer side of the vehicle body, where the peak and/or sidewall have a thickness larger than that of any other convex portion. Accordingly, the rigidity of the above convex portion is increased, thus improving durability of the circular shell durability.